I like this! I don't see any problem with it
Aside from the darker brick, which I don't know if I should read as a differently colored brick or as a hole...
(and make sure it looks nice when there are many of them next to each other
)
But in any case, this is more than enough quality for a Minecraft texture, I think (this is better than 99% of the textures out there)
If I were you, I'd start working on different ones (assuming you want to do the whole texture set), considering there are probably more than a hundred textures in the game
If you make any more, please post them as well; I'd like to see them!